The present invention relates to a method of inducing various states of consciousness in human beings. More particularly, the invention relates to a method of inducing such states of consciousness through generation of stereo audio signals having specific wave shapes which act as a carrier of a binaural beat. The resultant binaural beat acts to entrain brain waves into unique waveforms characteristic of identified states of consciousness. The invention is applicable in areas of learning and behavior replication as well as in the area of sleep inducement, and thus represents a significant departure from and improvement over known audio-based sleep inducement techniques, some of which will be discussed below.
The binaural beat phenomenon was discovered in 1839 by H. W. Dove, a German experimenter. Generally, this phenomenon works as follows. When an individual receives signals of two different frequencies, one signal to each ear, the individual's brain detects a phase difference or differences between these signals. When these signals are naturally occurring, the detected phased difference provides directional information to the higher centers of the brain. However, if these signals are provided through speakers or stereo earphones, the phase difference is detected as an anomaly. The resulting imposition of a consistent phase difference between the incoming signals causes the binaural beat in an amplitude modulated standing wave, within each superior olivary nucleus (sound processing center) of the brain. It is not possible to generate a binaural beat through an electronically mixed signal; rather, the action of both ears is required for detection of this beat.
FIGS. 1A and 1B show two superposed waves of different frequencies. FIG. 1C shows the resulting wave, which has a clear beat phenomenon. Assuming the two waves have equal amplitude but different respective frequencies f.sub.1, f.sub.2, the combination of the two waves may be represented mathematically as follows: ##EQU1##
The beat phenomenon arises from the variation in amplitude of a resulting carrier frequency. Pulses appear every 1/2(f.sub.1 -f.sub.2), with two maxima occurring each cycle, when cos(2.pi.)1/2[f.sub.1 -f.sub.2 ]=.+-.1. That is, the beat frequency is simply f.sub.1 -f.sub.2, a result which agrees with experience.
Known consciousness state inducing techniques have not used this binaural beat phenomenon, but have relied on other techniques, as follows. For example the use of audio generators to induce a state of consciousness known as sleep is well known in the prior art, as exemplified by U.S. Pat. No. 2,711,165 and 3,384,074. In one type of technique exemplified in these patents, generated audio signals include pleasing and harmonious study sounds or vibrations, fixed frequency signals which are buried cyclically with respect to amplitude, and repetitive sounds such as the falling of rain on the roof and the sighing wind through the trees.
U.S. Pat. No. 2,304,095 relates to a method of inducing sleep by generation of an audible or tactual signal which is related to the physiological process of heartbeat and respiration. In the disclosed method, the pitch and amplitude of a pleasing audio signal are varied at a rate somewhat slower than either the rate of heartbeat or the rate of respiration. As a result, heartbeat and respiration tend to synchronize with the audio signal, thus lowering heartbeat and respiration rates and inducing sleep.
Of course, there are other naturally-occurring sounds which have been recorded, and which are not varied, but which instead induce a state of relaxation which leads to sleep for a similar reason. For example, the pounding of waves on a shore line occurs at a frequency generally lower than that of heartbeat or respiration, and induces a state of relaxation.
The use of an electroencephalogram (EEG) as a research and diagnostic tool has led to findings that particular brain wave patterns are indicative of different states of consciousness. In 1934, researchers discovered that brain waves, and their associated states of consciousness, could be altered with repetitive visual stimulation at a known frequency, an effect known as entrainment. Scientific interest in entrainment continued throughout the 1960's. In the 1970's, numerous independent studies repeatedly confirmed that rhythmic flashing lights rapidly entrained brain waves.
A sonic equivalent of photic entrainment also is known, as disclosed for example in commonly-assigned U.S. Pat. No. 3,884,218, the inventor of which is the inventor of the present application. This patent discloses a method of inducing sleep in a human being by generating an audio signal which is made up of a familiar pleasing repetitive sound modulated by frequencies usually associated with an EEG sleep pattern. There are different EEG patterns related to various levels or depths of sleep, and it has been found that by modulating the repetitive sound with these different sleep patterns, it is possible to induce various levels of sleep. The inventor has coined the term frequency following response, or FFR, to describe this phenomenon.
Other known techniques for inducing various states of consciousness, or for performing brainwave analysis and related functions, are shown, for example, in the following U.S. patents:
______________________________________ 2,466,054 4,034,741 3,160,159 4,141,344 3,576,185 4,227,516 3,712,292 4,335,710 3,753,433 4,573,449 3,826,243 4,834,701 3,837,331. ______________________________________
The binaural beat phenomenon described above also can create a frequency entrainment effect. If a binaural beat is within the range of brain wave frequencies, generally less than 30 cycles per second, the binaural beat will become an entrainment environment. This effect has been used to study states of consciousness, to improve therapeutic intervention techniques, and to enhance educational environments. However, the modulation of the binaural beat signals with brain waves associated with particular activities has not been attempted previously.